1. Field of the Invention
This invention is related to the technical field of removing solids and H.sub.2 O from waste oil.
2. Description of the Prior Art
Efficient reconditioning of waste oils for reuse, so-called recycling, is advantageous from both economic and ecological points of view. Use of reconditioned or recycled oils (hereafter reprocessed waste oil) as fuel or propellant is subject to governmental regulation in most countries because impurities therein may be released into the atmosphere, creating an environmental hazard. In some cases, e.g., fuel oil applications, the impurity combustion products are most hazardous. Similar problems exist in other reprocessed waste oil applications, e.g., if they are used as base oil for the manufacture of lubricant oils.
The reprocessed waste oil impurities most commonly regulated for environmental reasons include inorganic and organic compounds of metals, sulfur, phosphorus, and the halogens, in particular chlorine. Limiting the concentration of these and other impurities is particularly important when the reprocessed waste oil is to be used as base oil for manufacturing lubricant oils. Emulsified water is also a commonly found contaminant in waste oil. If not removed, it reduces the economic value of the reprocessed oil, i.e., poor product appearance, potential for corrosion in equipment. Water contents in these oils can range from 1-90% by volume. Dirt, sand inorganics, etc. are agents that stabilize oil/H.sub.2 O emulsions.
One conventional method for reprocessing waste oils containing water and dissolved and undissolved solid contaminants, involves acid treatment of the waste oil followed by a separation and neutralization of the resultant acid phase, followed by neutralization and thermal treatment, in which remaining water is driven off by distillation. In certain applications the reprocessed waste oils themselves are subsequently distilled. Another conventional method is chemical treatment, i.e., demulsifiers, followed by phase separation with heat treatment.
U.S. Pat. No. 3,930,988 is directed to a method for the reduction of the ash and metals content in used lubricating oils in which the used oil is contacted with an aqueous solution of ammonium sulfate and/or ammonium bisulfate at about 93.degree. to 260.degree. C. and about 750 psig to react with the metal compounds present thus forming separable metal containing solids. The reaction mixture is separated into an aqueous phase containing the solids and an oil phase having reduced metals and ash contents.
U.S. Pat. No. 3,879,282 is directed to a method for decreasing the ash and lead content in used motor oils wherein the used oil is brought into contact with an aqueous solution of ammonium phosphate which forms insoluble metal salts which are allowed to settle as precipitate. Thereafter, an oil product phase is separated from the aqueous phase and precipitate.
U.S. Pat. No. 4,151,072 is directed to a method for reclaiming used lubricant oils regardless of contaminants or additive systems (impurities) contained therein, wherein, e.g., (a) used oil is contacted with an aqueous solution of an ammonium salt treating agent such as a salt selected from the group consisting of ammonium sulfate, ammonium bisulfate, ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate and mixtures thereof in appropriate quantities as a temperature of 60.degree. to 120.degree. C. (b) removing a major portion of the water and light hydrocarbons from the mixture of step (a) at a temperature of 110.degree. to 140.degree. C.; (c) separating the resulting oil phase by filtration; (d) heating the filtered oil phase to a temperature of 200.degree. to 480.degree. C. and contacting it with an adsorption agent. For some applications the resulting oil may be hydrogenated with hydrogen and a catalyst and then stripped at a temperature of 280.degree. to 395.degree. C.
The above-cited methods are either costly or otherwise lead to inefficient reprocessing of waste oils.